1. Field of the Invention
The present invention relates to a liquid discharge head for discharging liquid, such as ink, towards a recording medium. The present invention also relates to a recording device for recording, for example, an image onto a recording medium, such as a sheet material.
2. Description of the Related Art
A typical inkjet print head generally includes an ink container for holding ink; an exothermic element, i.e. a recording element, for discharging ink; and a duct for transferring ink to the exothermic element from the ink container.
Such a typical inkjet print head has a tendency to accumulate many air bubbles. These air bubbles are accumulated in the inkjet print head in several ways. For example, such an accumulation may be due to air entering the duct as a possible result of a change in the environment, or may be due to air bubbles remaining in the ink. Moreover, there are also cases where the air bubbles are generated due to exothermic heat or are formed in the process of fabrication of the inkjet print head. It is generally known that air bubbles inside the duct interfere with the flow of the ink being transferred to the exothermic element.
Air bubbles present on the main surface of the exothermic element can interfere with the formation of desired air bubbles, and moreover, an absorption effect generated by the undesired air bubbles reduces the pressure required for discharging the ink. This means that the ink cannot be discharged properly, thus leading to recording defects. Furthermore, if the air bubbles remain in the interior of an ink-supplying system, the ink cannot be sufficiently supplied to the exothermic element.
U.S. Pat. No. 5,812,165, for example, discloses a technique in which a groove is disposed inside a duct in order to prevent the ink supply from being interfered by air bubbles.
Furthermore, to reduce the air bubbles present in the interior of an ink-supplying system, the air bubbles, for example, may be removed by degassing the dissolved gas in the ink or may be prevented by providing a gas-liquid separation film in the ink-supplying system.
Moreover, to physically remove the air bubbles, the air bubbles, for example, may be removed by vacuuming the ink through ink discharge nozzles or by changing the components of the ink so as to allow easier defoaming of the air bubbles.
Removing the air bubbles by degassing the dissolved gas in the ink complicates the fabrication process of the inkjet print head. Moreover, according to this degassing technique, it is necessary to maintain a state where the air does not penetrate into the ink-supplying system during the actual use of the inkjet print head. This results in a complex structure of an ink cartridge. Moreover, this degassing technique is also problematic in that the air may enter through the ink discharge nozzles or through gaps between the components of the ink cartridge as time passes, meaning that maintaining the degassed state of the ink is extremely difficult.
On the other hand, providing the gas-liquid separation film requires a space in the ink-supplying system where the gas-liquid separation film is to be disposed. Moreover, an additional gas-liquid separation film must be disposed on the ink discharge nozzles in order to prevent air bubbles from entering through the nozzles.
Furthermore, removing the air bubbles by vacuuming the ink through the ink discharge nozzles is also problematic. In detail, although this technique can be effectively achieved by, for example, making the shape of a duct such that the duct is easily removable, since both the air bubbles and the ink are vacuumed at the same time, the vacuumed ink becomes a waste. Moreover, since the printer must be additionally provided with a holding component for holding the vacuumed ink and a vacuuming mechanism, the manufacture cost of the printer increases. Furthermore, depending on the structure of the vacuuming mechanism, there are cases where it is necessary to vacuum ink that contains no air bubbles. This may reduce the amount of ink that can actually be used and thus may lead to higher manufacturing costs.
According to U.S. Pat. No. 5,812,165 in which the duct is provided with a groove and has corners and edges, the capillary forces generated in the groove, the corners, and the edges may be significantly different from one another depending on how the inkjet print head is positioned during the printing process. For this reason, there are cases where the continuity of the ink-supplying path is lost.
Furthermore, if the amount of ink Q2 retained by the capillary forces of the edges and the corners become greater than the amount of ink Q1 transferred via the groove, the ink in the groove is drawn towards the corners. This may result in shortage of ink in the groove. Accordingly, the equation Q1>Q2 must constantly be satisfied. Moreover, since inkjet print heads developed in recent years move at an extremely high speed, a larger amount of ink is required per unit time, meaning that a larger amount of ink must be supplied to the inkjet print head. Accordingly, the amount of ink Q2 must also be larger.
However, retaining a larger amount of ink with the capillary forces of the edges and the corners can induce an adverse effect upon the ink-supplying path if the gas is present inside the duct. To solve this problem, more edges and corners are required. This, however, results in a complex structure of the ink container. It is therefore in great demand that a larger amount of ink be supplied stably with a simple structure.
Furthermore, depending on the tilt angle of the inkjet print head, there are cases where it is difficult to retain a sufficient amount of ink with the capillary forces generated in the edges.